Typically, automotive engines have engine power plants including a power train having at least a transmission and a differential, operationally coupled to each other, and engine exhaust systems including an exhaust pipe, a catalytic converter and a muffler. Such a power train is supported or held by a power plant frame directly secured to a car body to be installed on the automotive vehicle. However, the engine exhaust system is attached to the power plant frame so as to be suspended from the car body. In order to prevent engine vibration from being transmitted to the car body, flexible mounting members or elastic suspension members are used between the engine exhaust system and power plant frame. Such a suspension apparatus, including flexible mounting or elastic suspension members, is known from, for example, Japanese Utility Model application 61(1986)-36514, entitled "Suspension Apparatus For Engine Exhaust System," filed on Mar. 13, 1986 and laid open on Sep. 19, 1987 as Japanese Unexamined Utility Model Publication No. 62(1987)-148717.
In spite of the use of the elastic suspension members, however, since the engine exhaust system is directly suspended from the car body, the transmission of engine vibration to the car body through the engine exhaust system is not always completely prevented.
For the purpose of providing a brief technical background on eliminating the transmission of such vibration to the car body from the engine through the engine exhaust system, reference is made to FIGS. 1 to 4. An engine 2 is provided with and operationally, directly coupled to a power plant, having a transmission 3 and a differential 4 which are connected to each other and suspended by a power plant frame 5. The power plant frame 5 is firmly secured to the car body 10 (partly shown) in a well known manner. The engine 2 is further provided with and directly connected to an engine exhaust system, having an exhaust pipe 1 directly connected to the engine 2, a catalytic converter 11 disposed in the middle of the engine exhaust pipe 1 and a muffler 7 connected to an end of the exhaust pipe 1 remote from the engine 2. The engine exhaust system is suspended from the car body in such a way as to connect the exhaust pipe 1 to the power plant frame at two points, i. e., to the transmission 3 and the power plant frame 5 by elastic suspension members 6, and the muffler 7 directly to the car body 10 at front and rear ends of the muffler 7 by elastic suspension members 9.
A typical elastic suspension member, used as the elastic suspension members 6 and 9, is shown in FIG. 4. The elastic suspension members 6 and 9, which have the same structure and function as one another, comprise an elastic suspension block A made of, for instance an elastic rubber material, a sleeve-like metal spacer B, fitted in the elastic suspension block A and partly projecting from the elastic suspension block A, and a hanger arm or bracket C, attached to the elastic suspension bolt A by a bolt E and nut F through a heat insulation member D mounted on the projecting part of the spacer B.
Such an engine exhaust system suspension structure is apt to generate a great deal of stress at the juncture 1a between the exhaust pipe 1 and muffler 7 of the engine exhaust system, due to the phase difference of vibration between the power plant system and car body 10 as is shown in FIG. 2. The generation of such a great deal of stress causes damage to either one of or both the exhaust pipe 1 and muffler 7 at the juncture 1a.
For this reason, the exhaust pipe 1 could be improved so as to itself absorb engine vibration transmitted therethrough by utilizing, for instance, a flexible pipe 12, as part of the exhaust pipe 1, disposed between the catalytic converter 11 and muffler 7, as is shown in FIG. 3. The use of a flexible exhaust pipe such as pipe 12, however, increases the cost of engine exhaust system and causes somewhat troublesome installation operation of the engine exhaust system on the car body.